What is the principle of diffusion MRI?

Diffusion MRI measures the random movement of water molecules to create images of tissue microstructure.

Diffusion MRI is a non-invasive imaging technique that uses the random movement of water molecules to create images of tissue microstructure. The principle behind diffusion MRI is that water molecules in biological tissues are in constant motion due to thermal energy. This motion is known as Brownian motion, and it is influenced by the structure of the tissue. In regions where the tissue is tightly packed, such as in white matter, the movement of water molecules is restricted, while in regions where the tissue is less dense, such as in grey matter, the movement of water molecules is more free.

Diffusion MRI measures the diffusion of water molecules in different directions using a series of magnetic field gradients. By measuring the diffusion of water molecules in multiple directions, diffusion MRI can create a map of the diffusion tensor, which describes the direction and magnitude of water diffusion in each voxel of the image. This information can be used to infer the microstructure of the tissue, such as the orientation of axons in white matter.

Diffusion MRI has many applications in neuroscience, including the study of brain development, connectivity, and disease. It is also used in clinical settings to diagnose and monitor conditions such as stroke, multiple sclerosis, and brain tumors.